Conventionally, a plurality of cold-cathode tubes (CCFLs: Cold Cathode Fluorescent Lamps) are used for a backlight of a liquid crystal display in a liquid crystal television receiver (hereinafter referred to as a “liquid crystal TV”), a liquid crystal monitor, or the like (see, for example, Japanese Patent Application Laid-Open No. 2004-213994 (FIG. 1) (Patent document 1)). For example, in the liquid crystal TV having a screen size of about 30 inches, about 14 to 16 pieces of cold-cathode tubes are used.
FIG. 12 is a circuit diagram showing a conventional cold-cathode tube driving apparatus. In an apparatus shown in FIG. 12, N (N>1) pieces of cold-cathode tubes 104-1 to 104-N are provided. An inverter circuit 101 generates a high frequency voltage and N pieces of booster transformers 103-1 to 103-N boost the high frequency voltage generated by the inverter circuit 101 to apply the high frequency voltage after boosted to the N pieces of cold-cathode tubes 104-1 to 104-N. Note that the inverter circuit 101 detects conduction current values of the cold-cathode tubes 104-1 to 104-N based on drop voltages by resistances 105-1 to 105-N to supply gate signals in accordance with the values to current control FETs 102-1 to 102-N to thereby control the conduction current of the cold-cathode tubes 104-1 to 104-N. The current control FETs 102-1 to 102-N control the amount of the current conducted in the cold-cathode tubes 104-1 to 104-N in accordance with the gate signals from the inverter circuit 101.
In this manner, the N pieces of cold-cathode tubes 104-1 to 104-N are driven by the N pieces of booster transformers 103-1 to 103-N.
Patent document 1: Japanese Patent Application Laid-Open No. 2004-213994 (FIG. 1).